As an experienced sommelier and brewer, I can tell you that finding a substitute for amber malt can be a matter of personal preference and the specific characteristics you are looking for in your beer. One potential substitute that is often mentioned is melanoidin malt.
Melanoidin malt is essentially a more intense version of Munich malt. It is known for its rich, malty flavor and deep amber color. It adds a distinct toasty, biscuity character to beers and can contribute to a fuller body and mouthfeel. If you are looking for a substitute that will provide similar flavor and color characteristics to amber malt, then melanoidin malt can be a great choice.
However, it is important to note that melanoidin malt is not exactly the same as amber malt. Amber malt is typically lighter in color and has a slightly sweeter, caramel-like flavor. If you are specifically looking to replicate the exact flavor profile of amber malt, you may need to combine melanoidin malt with other malts to achieve the desired result.
In my personal experience, I have found that using a combination of melanoidin malt and caramel malt can help achieve a closer approximation to the flavor and color of amber malt. By blending these malts together, you can create a more complex malt profile that incorporates both the toasty, biscuity notes from the melanoidin malt and the sweet, caramel flavors from the caramel malt.
While melanoidin malt is often listed as a substitute for amber malt, it is important to consider your specific flavor and color requirements. Melanoidin malt can provide a similar intensity and richness to your beer, but if you are looking for an exact replication of amber malt, a combination of melanoidin malt and caramel malt may be necessary. Ultimately, the choice of substitute will depend on your personal preference and the specific characteristics you want to achieve in your brew.